PrimeGrid’sWoodall Prime Search
On 21 Dec 2007, 10:09:30 UTC, PrimeGrid’s Woodall Prime Search found the 33rdand largest known to date Woodall prime:

3752948*23752948-1
Woodall numbers are of the form: Wn=n.2n-1. Woodall numbers that are prime are called Woodall
primes. For more information, please see “Woodall prime” in The Prime Glossary(http://primes.utm.edu/glossary).

The prime is 1,129,757 digits long and will enter Chris Caldwell's “The Largest
Known Primes Database” (http://primes.utm.edu/primes) ranked 1st for Woodall
primes and 13th overall. It’s the first found mega-digit prime using LLR.
The discovery was made by Matthew J. Thompson of the United States using an Intel
P4 @ 2.8 GHz with 512 MB RAM. This computer took almost 15 hours and 11
minutes to complete the primality test.
The prime was verified on 24 Dec 2007, 1:10:44 UTC, by an AMD Athlon64 X23600+ with 2G GB RAM. This computer took a little over 24 hours 55 minutes totest.
The credits for the discovery are as follows:

1.
2.
3.
4.
5.

Matthew J. Thompson (United States), discoverer
PrimeGrid, et al.
MultiSieve, sieve program developed by Mark Rodenkirch
gcwsieve, sieve program developed by Geoff Reynolds
LLR, primality program developed by Jean Penné

The prime will be listed as 938237*23752950-1. This is 938237*2*2*23752948-1 which is3752948*23752948-1. Entry in “The Largest Know Primes Database” can be foundhere: http://primes.utm.edu/primes/page.php?id=83407
This is PrimeGrid’s third Woodall prime. Since the search began, just over 134,000
tests have been completed by 4524 users using 9149 computers.
Using a single PC would have taken years to find this prime. So this timely
discovery would not have been possible without the thousands of volunteers whocontributed their spare CPU cycles. A special thanks to everyone who contributed
their advice and/or computing power to the search - especially Brian Rodenkirk,Lennart Vogel, Joseph M. Osiecki, Geoffrey Reynolds, and Paul Underwood.
Additional thanks to all the sievers who prepared the work for PrimeGrid:
http://www.primegrid.com/orig/forum_thread.php?id=690
PrimeGrid’s Woodall Prime Search will continue to search for even larger WoodallPrimes. To join the search please visit PrimeGrid: http://www.primegrid.com

PrimeGrid’s
Woodall Prime Search
About PrimeGrid
Rytis Slatkevicius, the developer of PerlBOINC - a Perl-language-based port of theBOINC platform, created PrimeGrid as a test project for PerlBOINC. PrimeGrid’s first
sub-project was in cryptography as it participated in the RSA Factoring Challenge.
While it no longer participates in the challenge, PrimeGrid continues to expand its
functionality. Currently the project is running the following sub-projects:•••••

Primegen: generating a public sequential prime number database
Twin Prime Search: searching for gigantic twin primes of the form k*2n + 1
and k*2n - 1.
Cullen-Woodall Search: searching for mega primes of forms n*2n + 1 andn*2n - 1.
3*2^n-1 Search: searching for mega primes of the form 3*2n - 1.
Prime Sierpinski Project: helping Prime Sierpinski Project solve the Prime
Sierpinski Problem.

For more information, please visit PrimeGrid: http://www.primegrid.com
About BOINC
BOINC (Berkeley Open Infrastructure for Network Computing) is a software platform
for distributed computing using volunteered computer resources. It allows users toparticipate in multiple distributed computing projects through a single program.
Currently BOINC is being developed by a team based at the University of California,
Berkeley led by David Anderson.
For more information, please visit BOINC: http://boinc.berkeley.edu